Past and future are worlds we can never inhabit. We live of necessity in the present. But physicists and philosophers with very different outlooks, from Einstein to Derrida, claim the present is an illusion. Is time not a river at all, but instead a static dimension? Are we deluded by experience into imagining the present is real? Or are Einstein's spacetime universe, and Derrida's attack on the metaphysics of presence, fundamental errors?